This invention relates to foam control compositions for use in detergents. More particularly, this invention relates to foam control compositions which can inhibit foaming during post-wash rinsing operations, but which are able to do so without impairing the cleaning performance and still retain an appropriate level of foaming during the washing stage.
Soiled clothing is cleaned by introducing the clothing, a detergent composition, and water into a washing machine. The soil becomes dispersed in the water through the action of mechanical force and by affinity with the surfactant. The resulting waterborne soil dispersion is then discharged, and residual soil is subsequently rinsed out with fresh water. However, due to the strong foaming character of the surfactant (the cleaning component of the detergent composition), foaming can be quite persistent even during the rinse operation. This results in a number of shortcomings, such as requiring a larger number of rinses, lengthening the time required for the rinse operation, requiring large amounts of water, increasing the amount of waste water, and increasing power consumption.
In response to this, various foam control compositions for use in detergent applications have been disclosed with the goal of achieving an excellent cleaning performance while inhibiting foaming during the post-wash rinsing operation. For example, Japanese Patent Application Laid Open No. 2-230900 (230,900/1987), discloses a composition having a fatty acid soap as the base component. Japanese Patent Application Laid Open No. 3-269098 (269,098/1991), discloses a composition whose base components are polydimethylsiloxane and hydrophobic silica.
However the above compositions have several deficiencies. For example, large amounts of fatty acid soap must be present in order for the necessary foam-inhibiting performance to be developed. This not only conflicts with the goal of reducing the detergent volume, but also imparts a yellow cast to clothing while the undissolved residues stain the interior of the washing machine. Furthermore, in polydimethylsiloxane-based compositions, the foam-inhibiting activity is lost during the wash stage, which makes it very problematic to obtain good performance during rinsing. Although this system can give an acceptable performance during rinsing if the polydimethylsiloxane content is raised, this tactic causes excessive foam extinction during the washing stage, to the point that even the foam desirably exhibited by the detergent is almost completely extinguished.